Varian 23 EX加速器附加锥形束CT图像均匀性分析  

Evaluation on imaging uniformity of Varian 23 EX cone-beam CT

作　　者：张俊[1] 徐利明[2] 刘晖[1] 李炜澔[2] 全红[2] 

机构地区：[1]武汉大学中南医院放化疗科,湖北武汉430072 [2]武汉大学物理科学与技术学院,湖北武汉430072

出　　处：《中国医学影像技术》2011年第8期1703-1706,共4页Chinese Journal of Medical Imaging Technology

基　　金：国家自然科学基金(10875092)

摘　　要：目的分析Varian 23 EX加速器附加KV X线锥形束CT(CBCT)在不同扫描条件下图像均匀性的变化。方法采用安装在直线性加速器上的CBCT系统,在标准头/体部扫描条件下重复扫描体模,并将数据通过放疗网络传至计划系统及Matlab 7.0,利用Eclips计划系统评价获取图像在x、y及z轴方向上的均匀性变化,并与传统扇形束CT(FBCT)扫描重建图像的测量结果进行比较。结果 CBCT图像在标准头/体部扫描条件下,在三个轴向上均有良好的对称性和均匀性。在标准头部扫描方式下CT值的波动范围分别为:x轴±25 HU,y轴±30 HU,z轴±20 HU。在标准体部扫描模式下,CT值的波动范围略大。等中心横断面x,y轴方向上具有最佳的对称性和均匀性。相对于x,y轴方向,z轴具有更佳的对称性和均匀性。Bowtie滤过器能够明显减少模体散射线,可提高图像的均匀性。结论 Varian 23 EX加速器附加KV X线CBCT图像均匀度好,通过对CT值校正,CBCT可以用于治疗计划系统的剂量计算。Objective To analyze the variation of image quality in the domain of the uniformity while the scanning conditions of KV X-ray cone-beam CT（CBCT） was fixed on the Varian 23 EX linear accelerator.Methods Under the standard head/body part term,the phantom was successively scanned using CBCT fixed on the linear accelerator.The data were delivered to the TPS and Matlab 7.0 software via the radiotherapy network.The variation of imaging qualities in the domain of the uniformity on the x,y and z axis were obtained using the Eclips TPS evaluation.Then the results were compared with those obtained by the scanning reconstruction images of traditional fan-beam CT（FBCT）.Results The images of CBCT under the standard head/body part term had favorable symmetry and uniformity on the x,y and z axis.Under the standard head part term,the spatial fluctuant CT value ranges were ±25 HU on the x axis,±30 HU on the y axis and ±20 HU on the z axis,respectively.Under the standard body part term,the spatial fluctuant CT value ranges were a little bigger than those under the standard head part term.On the isocenter cross section of the x,y axis direction,both of the symmetry and uniformity were best.The z axis direction had better symmetry and uniformity than the other two axis directions.The Bowtie filter could obviously decrease the scattered ray and increase the images uniformity.Conclusion The imaging uniformity of KV X-ray CBCT fixed on the Varian linear accelerator is favorable.CBCT can be used in the treatment planning system dose calculation via correction of CT values.

关 键 词：锥形束CT 体模 图像均匀性 

分 类 号：R814.42[医药卫生—影像医学与核医学] R815.6[医药卫生—放射医学]